Abstract
We present a comprehensive study of CaCu$_3$Ru$_4$O$_{12}$ using bulk sensitive hard and soft x-ray spectroscopy combined with local-density approximation (LDA) + dynamical mean-field theory (DMFT) calculations. Correlation effects on both the Cu and Ru ions can be observed. From the Cu $2p$ core level spectra we deduce the presence of magnetic Cu$^{2+}$ ions hybridized with a reservoir of itinerant electrons. The strong photon energy dependence of the valence band allows us to disentangle the Ru, Cu, and O contributions and thus to optimize the DMFT calculations. The calculated spin and charge susceptibilities show that the transition metal oxide CaCu$_3$Ru$_4$O$_{12}$ must be classified as a Kondo system and that the Kondo temperature is in the range of 500-1000 K.
Highlights
We present a comprehensive study of CaCu3Ru4O12 using bulk sensitive hard and soft x-ray spectroscopy combined with local-density approximation þ dynamical mean-field theory (DMFT) calculations
Transition metal oxides show a wide variety of spectacular physical properties such as superconductivity, metal-insulator and spin-state transitions, unusually large magnetoresistance, orbital ordering phenomena, and multiferroicity [1–3]
One can observe that CCTO follows, far above its 25 K Neel temperature, almost a textbook Curie-Weiss law that can be understood in terms of paramagnetic S 1⁄4 1=2 Cu2þ ions
Summary
We present a comprehensive study of CaCu3Ru4O12 using bulk sensitive hard and soft x-ray spectroscopy combined with local-density approximation þ dynamical mean-field theory (DMFT) calculations. The presence of magnetic Cu ions immersed in an itinerant band leads to the emergence of Kondo physics, as demonstrated by our LDA þ DMFT results.
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